The Antey design represented the highest achievement of Soviet nuclear submarine technology. They were the second-largest attack submarines ever built, after the Typhoon-class submarine (Akula /Project 941).[2]:22–23 It was built to defeat an entire United States aircraft carrier group. A single Type 65 torpedo carried a 450 kg (990 lb) warhead powerful enough to sink an aircraft carrier.[3] Both missiles and torpedoes could be equipped with nuclear warheads. She was 9.1 m (30 ft) longer than the preceding Oscar I-class of submarines. The senior officers had individual staterooms and the entire crew had access to a gymnasium.[4][5]

The outer hull, made of high-nickel, high-chromiumstainless steel 8.5 mm (0.33 in) thick, had exceptionally good resistance to corrosion and a weak magnetic signature which helped prevent detection by U.S. magnetic anomaly detector (MAD) systems. There was a 200 cm (79 in) gap to the 50.8 mm (2.00 in)-thick steel pressure hull.[6] She was designed to remain submerged for up to 120 days. The sail superstructure was reinforced to allow it to break through the Arctic ice.[1]
The submarine was armed with 24 SS-N-19/P-700 Granit cruise missiles, and eight torpedo tubes in the bow: four 533 mm (21 in) and four 650 mm (26 in). The Granit missiles with a range of 550 km (340 mi), were capable of supersonic flight at altitudes over 20 km (12 mi). They were designed to swarm enemy vessels and intelligently choose individual targets which terminated with a dive onto the target.[4] The torpedo tubes could be used to launch either torpedoes or anti-ship missiles with a range of 50 km (31 mi). Her weapons included 18 SS-N-16 "Stallion" anti-submarine missiles.[1]

Kursk was part of Russia's Northern Fleet, which had suffered funding cutbacks throughout the 1990s. Many of its submarines were anchored and rusting in Zapadnaya Litsa Naval Base, 100 km (62 mi) from Murmansk.[7] Little work to maintain all but the most essential front-line equipment, including search and rescue equipment, had occurred. Northern Fleet sailors had gone unpaid in the mid-1990s.[1]

During her five years of service, Kursk completed only one mission, a six-month deployment to the Mediterranean during the summer of 1999 to monitor the United States Sixth Fleet responding to the Kosovo crisis.[8]:215 This was due to a lack of funds for fuel. As a result, many of her crew had spent little time at sea and were inexperienced.[2]

Kursk joined the "Summer-X" exercise, the first large-scale naval exercise planned by the Russian Navy in more than a decade,[9] on 10 August 2000. It included 30 ships including the fleet's flagship Pyotr Velikiy ("Peter the Great"), four attack submarines,[1] and a flotilla of smaller ships. The crew had recently won a citation for its excellent performance and been recognized as the best submarine crew in the Northern Fleet.[10] While it was on an exercise, Kursk loaded a full complement of combat weapons. It was one of the few ships authorized to carry a combat load at all times.

On the first day of the exercise, Kursk successfully launched a Granit missile armed with a dummy warhead.[1] Two days later, on the morning of 12 August, Kursk prepared to fire dummy torpedoes at the Kirov-class battlecruiserPyotr Velikiy (Peter The Great). These practice torpedoes had no explosive warheads and were manufactured and tested at a much lower quality standard.[11] On 12 August 2000, at 11:28 local time (07:28 UTC), there was an explosion while preparing to fire.[12] The Russian Navy's final report on the disaster concluded the explosion was due to the failure of one of Kursk's hydrogen peroxide-fueled Type 65 torpedoes.[13] A subsequent investigation concluded that high-test peroxide (HTP), a form of highly concentrated hydrogen peroxide used as propellant for the torpedo, seeped through a faulty weld in the torpedo casing.[14] When HTP comes in contact with a catalyst, it rapidly expands by a factor of 5000, generating vast quantities of steam and oxygen. The pressure produced by the expanding HTP ruptured the kerosene fuel tank in the torpedo and set off an explosion equal to 100–250 kilograms (220–550 lb) of TNT. The submarine sank in relatively shallow water, bottoming at 108 metres (354 ft) about 135 km (84 mi) off Severomorsk, at 69°40′N37°35′E﻿ / ﻿69.667°N 37.583°E﻿ / 69.667; 37.583. A second explosion 135 seconds after the initial event was equivalent to 3-7 tons of TNT.[15] The explosions blew a large hole in the hull and collapsed the first three compartments of the sub, killing or incapacitating all but 23 of the 118 personnel on board.[8]:208

Though the British and Norwegian navies offered assistance, Russia initially refused all help.[16] All 118 sailors and officers aboard Kursk died. The Russian Admiralty initially told the public that the majority of the crew died within minutes of the explosion, but on 21 August, Norwegian and Russian divers found 24 bodies in the ninth compartment, the turbine room at the stern of the boat. Captain-lieutenant Dmitri Kolesnikov wrote a note listing the names of 23 sailors who were alive in the compartment after the ship sank.

Kursk carried a potassium superoxide cartridge of a chemical oxygen generator, used to absorb carbon dioxide and chemically release oxygen during an emergency. However, the cartridge became contaminated with sea water and the resulting chemical reaction caused a flash fire which consumed the available oxygen. The investigation showed that some men temporarily survived the fire by plunging under water, as fire marks on the bulkheads indicated the water was at waist level at the time. Ultimately, the remaining crew burned to death or suffocated.[17]

Russian President Vladimir Putin, though immediately informed of the tragedy, was told by the navy that they had the situation under control and rescue was imminent. He waited five days before he ended his holiday at a presidential resort in Sochi on the Black Sea. Only four months into his tenure as President, the public and media were extremely critical of Putin's decision to remain at a seaside resort, and his highly favourable ratings dropped dramatically.[18] The President's response appeared callous and the government's actions looked incompetent.[19] A year later he said, "I probably should have returned to Moscow, but nothing would have changed. I had the same level of communication both in Sochi and in Moscow, but from a PR point of view I could have demonstrated some special eagerness to return."[20]

A consortium formed by the Dutch companies Mammoet and Smit International[21] was awarded a contract by Russia to raise the vessel, excluding the bow. They modified the barge Giant 4 which raised Kursk and recovered the remains of the sailors.[22]

During salvage in 2001, the team first cut the bow off the hull using a tungsten carbide-studded cable. As this tool had the potential to cause sparks which could ignite remaining pockets of reactive gases, such as hydrogen, the operation was carefully executed. Most of the bow was abandoned and the rest of the vessel was towed to Severomorsk and placed in a floating dry dock for analysis.

The remains of Kursk's reactor compartment was towed to Sayda Bay on Russia's northern Kola Peninsula – where more than 50 reactor compartments were afloat at pier points – after a shipyard had defuelled the boat in early 2003.[23]

Some torpedo and torpedo tube fragments from the bow were recovered and the rest was destroyed by explosives in 2002.

Notwithstanding the navy's oft-stated position that a collision with a foreign vessel had triggered the event, a report issued by the government attributed the disaster to a torpedo explosion caused when high-test peroxide (HTP), a form of highly concentrated hydrogen peroxide, leaked from a faulty weld in the torpedo's casing.[3][10][24] The report found that the initial explosion destroyed the torpedo room compartment and killed everyone in the first compartment.[25][26] The blast entered the second and perhaps the third and fourth compartments through an air conditioning vent. All of the 36 men in the command post located in the second compartment were immediately incapacitated by the blast wave and possibly killed.[27] The first explosion caused a fire that raised the temperature of the compartment to more than 2,700 °C (4,890 °F).[28] The heat caused the warheads of between five and seven additional torpedoes to detonate, creating an explosion equivalent to 2–3 tons of TNT[29] that measured 4.2 on the Richter magnitude scale on seismographs across Europe[30] and was detected as far away as Alaska.[31]

Vice-Admiral Valery Ryazantsev differed with the government's official conclusion. He cited inadequate training, poor maintenance, and incomplete inspections that caused the crew to mishandle the weapon.[32] During the examination of the wrecked sub, investigators recovered a partially burned copy of the safety instructions for loading HTP torpedoes, but the instructions were for a significantly different type of torpedo and failed to include essential steps for testing an air valve. The 7th Division, 1st Submarine Flotilla never inspected Kursk's crew's qualifications and readiness to fire HTP torpedoes.[26]Kursk's crew had no prior experience with HTP-powered torpedoes and had not been trained in handling or firing HTP-powered torpedoes. Due to their inexperience and lack of training, compounded by incomplete inspections and oversight, and because the Kursk's crew followed faulty instructions when loading the practice torpedo, Ryazantsev believes they set off a chain of events that led to the explosion.[2][33]